Need help in threading

//This is simple example of thread using 
// on Form1 - only Label And Textbox - I hope, you know how to add event handlers from Designer...
 using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Threading;

namespace ThreadTakesDataFromString
{
    public partial class Form1 : Form
    {
        Thread m_OtherThread;
        string masterCommand;
        public Form1()
        {
            InitializeComponent();
            m_OtherThread = new Thread(new ThreadStart(HardWork));
            m_OtherThread.Start();
        }

        private void HardWork()
        {
            string currentCommand = "";
            while (masterCommand != "exit")
            {
                if (currentCommand != masterCommand)
                {
                    SetText(label1, "I have got <" + masterCommand + ">");
                    currentCommand = masterCommand;
                }
                else
                {
                    SetText(label1, "Continue work!");
                }
                Thread.Sleep(400);
            }
        }

        delegate void OnTextChange(Label labelForChange, string moreText);
        void SetText(Label labelForChange, string moreText)
        {
            if (labelForChange.InvokeRequired)
            {
                OnTextChange tsDelegate = new OnTextChange(SetText);
                labelForChange.Invoke(tsDelegate, new object[] { labelForChange, moreText });
            }
            else
            {
                if (label1.Text.Length > 300)
                {
                    label1.Text = "";
                }
                label1.Text += moreText+ "\n";
            }
        }

        private void textBox1_TextChanged(object sender, EventArgs e)
        {
            masterCommand = textBox1.Text;
        }

    }
}